The invention relates to an apparatus and to a method for the sensing of objects moved through the field of view of an optical sensor comprising a device for the selection of regions of interest which are each only associated with a part of the field of view of the optical sensor.
With apparatus or methods of this type, which use camera systems for example, it is frequently necessary to evaluate the sensed image data in real time or at least at very high speed, which has the consequence that a high calculating power must be available to the evaluation system, which is associated with a corresponding economic effort. To reduce the required calculating power, it is known to identify those regions of the recorded images which are of special interest by means of a pre-processing stage prior to the actual evaluation of the sensed image data. Regions of interest of this type are as a rule known as “ROIs” (regions of interest).
After the ROIs have been defined by means of the pre-processing stage, it is possible to limit oneself within the framework of the actual evaluation circuit only to processing the sensed image data of these ROIs, which requires correspondingly less calculating power than the processing of the complete images recorded by the optical sensor or by the camera.
In accordance with the prior art, the ROIs are determined via a pre-processing of the complete sensed image data, with simple algorithms being used here due to the high image data flow which, for example, only determine whether the gray value of a pixel lies above a predetermined threshold value. If this is the case, the checked pixel is associated with an ROI; otherwise, it is not taken into account in the further evaluation. Algorithms of this type suffer, among other things, from the disadvantage that the respective condition—in the aforesaid example the exceeding of a predetermined threshold value—is not always reliably satisfied since, for example, an object of interest to be sensed is not necessarily always brighter than the background surrounding the object. In cases of this type, the said algorithms cannot be used or can only be used with restrictions.